What can you leave as a reward for AFTER a certain amount of studying is done?

Keep in mind...

People often cut back on sleep or exercise time when they need more time for studying. The problem with this is sleep and exercise are unusual activities in the sense that, because of their positive impact on our mind, in appropriate, moderate amounts, they actually give us MORE time of productive studying. So, be mindful of that when considering whether you want them to be the activities you cut back on.